1. Technical Field
The present invention relates to an acceleration switch and an electronic device including the acceleration switch.
2. Background Art
As a conventional acceleration switch, an omnidirectional acceleration switch in which a counter electrode is provided inside amass body and the mass body is supported by a plurality of beams is described with reference to FIG. 19. FIG. 19 is a top view of the conventional acceleration switch. This acceleration switch 100 includes a peripheral portion 101, four beams 102 to 105, a mass body (weight) 106, and a counter electrode 107. One end of the mass body is supported by the four beams, which are fixed to the peripheral portion. In accordance with acceleration applied to the acceleration switch, the mass body and the counter electrode disposed inside the mass body are brought into contact with each other. In this manner, an external device connected to the acceleration switch detects vibration. This acceleration switch has various advantages such as being available as a normally-off and omnidirectional switch and being relatively compact and mass-producible because monocrystalline silicon can be used as abase for production with the use of semiconductor manufacturing technology.
If the acceleration switch is mounted in, for example, a portable device which can incorporate only a small capacity battery to save power, the device can stop its operation when a human vibration is not detected, that is, when the device is not used, and the device can automatically start its operation upon detection of vibration, that is, when the device is used. Thus, it is possible to realize an electronic device in which the wasted use of a battery is avoided.
On the other hand, in an acceleration switch which detects vibration based on applied acceleration and turns ON and OFF the device, it is desired to uniformly detect vibration in any direction, and hence an omnidirectional switch is advantageous. Accordingly, as described in Patent Literature 1, it is desired to support a weight (mass body) by a plurality of beams so that the vibration of the weight may not be one-sided depending on the acceleration.
Such acceleration switch to be mounted on a portable device is highly required to be more compact, and hence a smaller external dimension of the acceleration switch is more advantageous. Cost of the acceleration switch is also highly required to be lower, and it is therefore further advantageous to use the semiconductor manufacturing technology to reduce the external dimension of the acceleration switch and thereby produce a large number of acceleration switches on a single wafer.